1. Field of the Invention
The present invention relates to a transfer system, and particularly relates to a transfer system that transports articles in and out of processing devices without causing the processing devices to wait.
2. Description of the Related Art
There is need for articles such as front opening unified pods (FOUPs: sealed cassettes for transporting semiconductor wafers) to be transported in and out of load ports of processing devices such as semiconductor processing devices and semiconductor inspection devices without causing the processing devices to wait. In view of this, it has been proposed to provide a buffer in the vicinity of processing devices, and provide additional transfer devices for performing transport between the buffers and the processing devices. For example, according to Patent Document 1 (JP 2006-224944A), a plurality of tracks for overhead travelling vehicles are arranged in parallel in a ceiling space, one of which is used for long-distance transport, and another of which is used for short-distance transport. Buffers are disposed under the track for long-distance transport, and load ports of processing devices are disposed under the track for short-distance transport. The overhead travelling vehicles for long-distance transport deliver and receive articles to and from the buffers, and the overhead travelling vehicles for short-distance transport deliver and receive articles between the buffers and the load ports. However, this formation makes the arrangement of a plurality of tracks in front of the processing device unavoidable.
According to Patent Document 2 (JP 2005150129A), buffers including a transfer device are provided in front of processing devices, overhead travelling vehicles deliver and receive articles to and from the buffers, and the transfer device in the buffer delivers and receives articles to and from the load port. However, a display for indicating the operation state, an operation panel for manual operation, and the like are provided on the front surface of the processing device, and it is not preferable for them to be blocked by the buffer. Furthermore, the load port is used not only by an automatic transfer device, but also for manual transport, and manual access is difficult if the front surface of the processing device is covered by the buffer.